The cAMP mediated second messenger pathway is a well established model of gene regulation. Within a given cell, many transcription factors are known to interact with and work through the protein kinase A/CREB pathway making integration of multiple signals through common regulatory factors an exceedingly complex phenomenon. The mechanism by which CBP (a CREB co-activator) influences gene regulation is not fully understood, but it is likely that this factor contributes to transcriptional signal integration. There is increasing evidence that this activity may be, in part, due to histone acetylation (HAT) of chromatin that exposes DNA for transcription. The main thrust of this project is to characterize the intrinsic HAT activity of CBP/p300. Four Specific Aims are proposed: (1) CBP/p300 proteins mutated in the putative intrinsic HAT domain (between the bromodomain and the glutamine-rich region of CBP/p300) will be developed to determine and test whether they retain their intrinsic HAT activity. This will also be helpful in mapping the HAT domain. (2) To test whether the intrinsic HAT activity of CBP/p300 for nucleosomes and polynucleosomes is blocked by E1A, since the mechanism by which adenovirus 12S E1A blocks the CBP/p300 co-activator is unknown. (3) To determine whether mutants lose their ability to activate reconstituted chromatin (DNA bound to histones), yet maintain their ability to activate transcription in DNA not bound to histones. (4) To study CBP HAT mutants in developing flies. This lab has previously shown that dCBP rescues CBP-null flies. The inability of CBP HAT mutants to rescue CBP-null flies would be strong evidence that intrinsic HAT activity of CBP (and p300) is critical for in vivo function, and that histone acetylation plays a central role in their gene regulatory function. Gaining insight to the mechanisms of gene activation and silencing has far reaching relevance in the treatment of many diseases including cancers and endocrinopathies. Through a mentored career development plan, the Principal Investigator will gain an enhanced capacity to be productive in the field of molecular biology with a focus on gene regulation. This will be accomplished by conducting the above described research, attending and presenting at local and national seminars and meetings, and participating in courses teaching molecular biology techniques. The proposed mentoring laboratory and institution are rich in intellectual and physical facility resources that provide an excellent environment for the Principal Investigator to transition to independence in the design and implementation of research in the field of gene regulation.